Brainstorming is an group based idea generation technique which helps to reveal many solution alternatives in a short period of time.

Wireframe is a layout or low fidelity structural representation of your product which gives a rough idea how it will look.

Persona is a fictional characters which is based on the research and represent the need of a potential users.

Prototyping is the process of making the simulation or sample version of the real product in order to test it and get feedback.

Observation is a process of watching and listening carefully to users in their real context during their natural activity.

Affinity map is a visual data sorting and grouping tool for organizing the information which you abtain at the end of the different sessions.

You are asking questions and try to learn from the user about the subject which you work on.